On the Performance of DF Opportunistic Relaying Systems with Limited Feedback

In this paper the performance of decode-and-forward (DF) opportunistic relaying systems with limited feedback is studied. Firstly an approximate expression of outage probability for limited-feedback opportunistic relaying is derived. Secondly the diversity gain with limited feedback is proved to be only 2 regardless of the number of potential relays or feedback accuracy, which differs from the full-diversity gain achieved by the ideal opportunistic DF relaying. Moreover, further analysis shows that with the increasing accuracy of feedback, the outage probability will approach to that of the ideal opportunistic relaying. Based on the theoretical results, a feedback method is developed to determine the minimum number of feedback bits with the outage loss under control. Simulation results confirm the theoretical analyses.